biochem exam 3

living organisms require input of free energy:

1) mechanical work
2) active transport
3) synthesis of macromolecules

phototrophs

obtain energy from light

Chemotrophs

obtain energy through the oxidation of carbon fuels

Catabolism

Metabolic pathways that break down molecules, releasing energy.

anabolism

Metabolic pathways that construct molecules, requiring energy.

reduced molecules are

energy rich

oxidized molecules are

energy poor

are carbohydrates or fats a more efficient fuel source

fats, the carbons are more reduced

Stage 1 of catabolism

-Large molecules in food are broken into smaller units.
-This is a preparation stage; no useful energy is captured.

stage 2 of catabolism

-Small molecules are degraded to a few simple units that play a central role in metabolism.
-Most of molecules are converted into acetyl CoA. Some ATP is generated (small amount).

stage 3 of catabolism

ATP is produced from the complete oxidation of acetyl CoA (citric acid cycle + oxidative phosphorylation)

Thermodynamically \___ reactions can be driven by \___ reactions

unfavorable, favorable

\___ is universal currency of free energy

ATP

ATP hydrolysis drives metabolism by

shifting the equilibrium constants of coupled reactions

metabolic pathway criteria

1) the individual reactions must be specific
2) the pathway in total must be thermodynamically favorable

metabolic pathway

A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds.

Phosphate can be transferred from compounds with

higher free energy change to those with lower free energy change

Molecules with higher phosphoryl-transfer potential than ATP

1) Phosphoenolpyruvate (PEP)
2) 1,3-Biphosphoglycerate (1,3-BPG)
3) Creatine Phosphate

Muscle contains only enough ATP to power muscle contraction for

less than 1 second

Creatine phosphate can

regenerate ATP from ADP

activated carriers

small molecules carrying activated functional groups that can be donated to another molecule

ATP is an activated carrier of

phosphate groups

Coenzyme A is an activated carrier of

two-carbon fragments (acyl groups)

NAD+ and FAD are activated carriers of

electrons for fuel oxidation

NADPH

activated carrier of electrons for the synthesis of biomoleucles

Reduced organic compounds serve as

fuels from which electrons can be stripped off during oxidation

carbon atoms in fuels

are oxidized to yield CO2

The \___ is the same in NADP+ and NAD+

reactive site

NAD+ and NADP+

-common redox cofactors
-can dissociate from the enzyme after reaction

Importance of glucose

-excellent fuel
-can be efficiently stored in polymeric form
-versatile biochemical precursor

Stage 1 of glycolysis

traps glucose in the cell and modifies it so that it can be cleaved into a pair of phosphorylated 3-carbon compounds (prep stage)

Stage 2 of glycolysis

oxidizes the 3-carbon compounds to pyruvate while generating 2 molecules of ATP (payoff stage)

Glycolysis Stage 1 reactions

glucose -\> glucose 6-phosphate -\> fructose 6-phosphate -\> fructose 1,6-bisphosphate -\> glyceraldehyde 3-phosphate and dihydroxyacetone phosphate

Glycolysis stage 2 reactions

glyceraldehyde 3-phosphate -\> 1,3-bisphosphoglycerate -\> 3-phosphoglycerate -\> 2-phosphoglycerate -\> phosphenolpyruvate -\> pyruvate

What steps of glycolysis require input of ATP

1, 3

what steps in glycolysis produce ATP

6, 10

What steps of glycolysis are irreversible?

1,3, 10

what enzyme catalyzes reaction of glucose to glucose 6-phosphate

hexokinase

what enzyme catalyzes reaction of glucose 6-phosphate to fructose 6-phosphate

phosphoglucose isomerase

what enzyme catalyzes reaction of fructose 6-phosphate to fructose 1,6-bisphosphate

phosphofructokinase

what enzyme catalyzes reaction of fructose 1,6-bisphosphate to glyceraldehyde 3-phosphate and dihydoxyacetone phosphate

aldolase

what enzyme catalyzes the reversible reaction of dihydroxyacetone phosphate to glyceraldehyde 3-phosphate

triose phosphate isomerase

what enzyme catalyzes the reaction of glyceradehyde 3-phosphate to 1,3-BPG

glyceraldehyde 3-phosphate dehydrogenase

what enzyme catalyzes the reaction of 1,3-BPG to 3-phosphoglycerate

phosphglycerate kinase

what enzyme catalyzes the reaction of 3-phosphoglycerate to 2-phosphoglycerate

phosphoglycerate mutase

what enzyme catalyzes the reaction of 2-phosphoglycerate to PEP

enolase

what enzyme catalyzes the reaction of PEP to pyruvate

pyruvate kinase

glucose

glucose 6-phosphate

fructose-6-phosphate

fructose 1,6-bisphosphate

Glyceradehyde 3-phosphate

dihydroxyacetone phosphate

1,3-bisphosphoglycerate

3-phosphoglycerate

2-phosphoglycerate

phosphoenolpyruvate (PEP)

pyruvate

Phosphofructokinase (PFK) is

highly regulated:
-activity increases when ATP is low or ADP/AMP is high
-inhibited when cell has high ATP

NAD and NADP are

common redox cofactors

what process drives the last step of glycolysis

tautomerization of pyruvate from enol form to keto form

Pyruvate tautomerization

drives ATP production

glucose is the only carbohydrate that feeds into glycolysis

false

What other carbohydrates can be used in glycolysis

glycogen, starch, disaccharides, hexose

What causes lactose intolerance?

deficiency of lactase

how many glucose molecules are used in glycolysis

1 glucose

how many ATP molecules are used for glycolysis

2 ATP

how many NAD+ molecules are used for glycolysis

2 NAD+

How many pyruvate molecules are made from 1 glucose molecule?

2 pyruvate

How many ATP are produced in glycolysis?

4 are formed, but 2 are used during glycolysis reactions, so net gain is 2.

How many NADH are produced by glycolysis?

2 NADH

Fates of pyruvate from glycolysis

acetaldehyde, lactate, acetyl CoA

what enzyme catalyzes lactic acid fermentation

lactate dehydrogenase

lactate dehydrogenase requires what cofactor

NADH

How many steps does alcohol fermentation have

2 steps

what is the intermediate of ethanol fermentation

acetaldehyde

what enzyme catalyzes the first step of ethanol fermentation

pyruvate decarboxylase

what enzyme catalyzes the second step of ethanol fermentation

alcohol dehydrogenase

what molecule is produced in the first step of ethanol fermentation

CO2

The CO2 produced in ethanol fermentation is responsible for

carbonation in beer

do humans use ethanol fermentation

no

do humans produce pyruvate decarboxylase

no, this is why ethanol fermentation does not occur

do humans produce alcohol dehydrogenase

yes, for the metabolism of ethanol from drinking

glycolysis captures all of the energy available in glucose

false, it captures very little

cellular respiration

complete oxidation of organic fuels to CO2 and H2O in the presence of O2

products of cellular respiration

carbon dioxide, water, and ATP

Which produces more ATP, glycolysis or cellular respiration

cellular respiration

Stages of Cellular Respiration

glycolysis, the citric acid cycle, and oxidative phosphorylation

what fuels can be used to produce acetyl CoA

amino acids, fatty acids, glucose, pyruvate

What step of cellular respiration produces the most ATP?

oxidative phosphorylation

where in the cell is acetyl CoA produced

mitochondria

Where in the cell does glycolysis occur?

cytoplasm

where in the cell does the CAC occur

mitochondrial matrix

where in the cell does oxidative phosphorylation occur?

inner membrane of the mitochondria

What is the fuel for the citric acid cycle

Acetyl CoA

what reaction is used to convert pyruvate to acetyl CoA

oxidative decarboxylation

what enzyme is involved in the conversion of pyruvate to acetyl CoA

pyruvate dehydrogenase complex

What coenzymes are required by the pyruvate dehydrogenase complex

prosthetic groups: TPP, lipoyllysine, FAD
co-substrates: NAD+, CoA-SH

how many enzymes make up the pyruvate dehydrogenase complex

3 (E1, E2, E3)

Is the synthesis of acetyl CoA from pyruvate reversible?

no, irreversible